It is well known that any significant reduction or restriction in the flow of blood through the arteries of the body can cause complications which may have serious ischemic consequences. Arterial blockages caused by plaque and fibrotic stenosis in coronary arteries are known to be a leading cause of heart attacks, subsequent strokes, and other debilitating maladies. Accordingly, it is extremely important for the health of a patient that any stenosis, or blockage, which is causing such a condition, be eliminated or reduced.
With the advent of bypass surgery techniques commonly known as CABG, the ischemic consequences of blockages in arterial segment can be alleviated by grafting around the lesion site a replacement means, typically with a saphenous vein graft. In this manner, blood is allowed to bypass the blockage in the affected artery and the blood supply to the body tissues downstream from the blockage is thereby restored. While bypass surgical procedures have become relatively safe, reliable, and effective, portions of the body must nevertheless be opened to accomplish the surgery. In other words, bypass surgery is invasive, and can consequently require significant post-operative recovery time. To avoid the drawbacks associated with invasive bypass surgery, less invasive surgical procedures have been developed wherein a device is inserted into the bloodstream of a patient and advanced into an artery to reduce or remove an arterial stenosis.
One well known and frequently used procedure to accomplish this task is popularly known as angioplasty. For a basic angioplasty procedure, a dilating balloon is positioned across the particular stenotic segment and the balloon is inflated to open the artery by breaking up and compressing the plaque which is creating the stenosis. The plaque, however, remains in the artery and is not removed. Unfortunately, in some cases, it appears that the plaque which remains in the artery may still present a stenosis. Furthermore, in approximately 30-60% of the vessels treated by angioplasty, there is a restenosis. This high recurrence rate is thought to be the result of fibrotic contraction in the lumen of the vessel.
A further alternative treatment method involves percutaneous, intraluminal installation of one or more expandable, tubular stents or prostheses in sclerotic lesions. Stents or prostheses are known in the art as implants which function to maintain patency of a body lumen in humans and especially to such implants for use in blood vessels. They are typically formed from a cylindrical metal mesh which expand when internal pressure is applied. Alternatively, they can be formed of wire wrapped into a cylindrical shape. The present invention relates to an improved stent design which by its specifically configured struts can facilitate the deployment and embedment of the stent within a vessel and is constructed from a manufacturing process which provides a controlled and superior stress yield point and ultimate tensile characteristics.
Stents or prostheses can be used in a variety of tubular structures in the body including, but not limited to, arteries and veins, ureters, common bile ducts, and the like. Stents are used to expand a vascular lumen or to maintain its patency after angioplasty or atherectomy procedures, overlie an aortic dissecting aneurysm, tack dissections to the vessel wall, eliminate the risk of occlusion caused by flaps resulting from the intimal tears associated with primary interventional procedure, or prevent elastic recoil of the vessel.
These metallic stents are deployed inside an arterial segment and embedded in the vessel to maintain patency typically after angioplasty or atherectomy interventions. Once they are so positioned, they are extremely difficult to remove. Often the vessels in which they are placed become occluded or severely restenosed in a relative short period of time. These complications continue to occur the longer the stents remain in place, resulting in total or partial obstruction of blood flow through the artery. Usually, the distal portion of the artery will remain patent and is supplied by collateral circulation through branches of other major arteries. However, tile decreased direct blood flow results in many cardiac problems.
It has also been shown that when an angioplasty procedure is performed after the stenotic segment is longitudinally incised, the opening established through the segment is much larger as compared to standard angioplasty without the prior incisions. Still further, the increase in the opening in the stenotic segment is accomplished without tearing the vessel wall. Moreover, it has been found that incising the stenosis prior to dilation allows greater compression of the stenotic tissue with decreased likelihood of the stenosis rebuilding at a later date. As those skilled in the art will appreciate, the plaque creating a common arterial stenosis is somewhat fibrous and will tend to return to its original predilation configuration. With this fibrous composition, the stenosis is therefore more likely to maintain a compressed configuration if the fibers are incised prior to balloon dilation. On the other hand, if the fibers in the stenosis is not incised first, the completeness of the compression of the stenosis is dependent on whether the inflated balloon is able to break apart fibers in the tissue as those skilled in the art will recognize, dilation of a segment is of course limited by the arteries able to withstand dilation. Over-dilation can have the catastrophic result of rupturing the vessel.
In light of the above, it is an object of the present invention to provide an improved device and method for cutting a previously deployed and embedded stent within an arterial stenosis and additionally longitudinally incising the stenotic segment to enhance blood flow.
It is another object of the present invention to provide a cutting device which, in cooperation with an angioplasty procedure, is able to produce an opening in a stenotic segment where the diameter of the opening is greater than the insertion diameter of the device.
It is also an object of the present invention to provide a device which allows improved control over the length of the incisions produced in the stenotic segment
Yet another object of the present invention is to provide a device which is flexible enough to allow advancement of the device through narrow vessels and around sharp turns.
Still further, it is an object of the present invention to provide a device for longitudinally incising a stenotic segment of an artery which is relatively easy to manufacture and is comparatively economical.